**Bonk**

Expression used by cyclists to describe exercise induced low blood sugar levels; being a feeling of light-headedness and weakness in all limbs. 

Similar to **The Wall** in running. Has fallen out of usage in recent years due to alternative meanings. 

The cure is to stop riding and eat something sweet.  Water and electrolyte won't help.  You also need to rest for a while.

Also known as Crashing, Blowing Up, or Running out of Steam/Gas/Fuel, or Empty Tank.   

Its not a pleasant feeling, and should be avoided by eating regularly on long rides.